International Application No. WO 92/03740 describes an acceleration sensor which is produced on a substrate by means of surface micromechanics. The sensor has a movable seismic mass which is suspended from a thin bending element in such a way that it can be displaced by an acceleration parallel to the surface or the substrate. Fastened to the seismic mass are movable electrodes which are arranged between fixed electrodes, the fixed electrodes being anchored on the substrate. Consequently, the distances between the movable electrodes and the fixed electrodes are varied by an acceleration, and this leads to a change in the capacitance between the electrodes. The evaluation of the change of this capacitance is then a measure of the acceleration.
The fixed electrodes have a first and a second group, the electrodes of the first group being arranged on one side of the movable electrodes, and the second group of fixed electrodes being arranged on the other side of the movable electrodes. The electrodes of the individual groups are respectively electrically connected in parallel. The fixed electrodes are respectively anchored individually on the substrate. The electrical contacting of the individual fixed electrodes is performed by conductor tracks which are diffused into the silicon substrate.
In such sensors, very small changes in capacitance have to be detected. Conductor tracks which are arranged in the immediate vicinity of one another have large stray capacitances. Furthermore, conductor tracks, in particular diffused conductor tracks, have a certain resistance value, which can impede the measurement of small capacitances. It is therefore desirable to use approximately the same resistance value for the conductor track for all fixed electrodes of a group.